The present invention relates to a process and an apparatus for the detection of molecular or ionic species by a mechanism involving charge transfers.
More specifically it relates to detectors having as active molecules, molecules able to transfer or receive a charge when in contact with the molecular or ionic species to be detected. The operating principle of these detectors is consequently based on redox reactions. The latter can lead to a modification of the electrical conductivity and/or color of the active molecules and this modification can be registered by conventional electrical resistance or optical absorption measuring means.
For some years, detectors of this type have been developed for checking the presence in a gas of molecular species, such as NO.sub.2. The article by S. Baker et al published in IEE Proceedings, vol. 130, Part I, no. 5, Oct. 1983, pp. 260-263 illustrates a detector of this type, in which the active molecule is constituted by a copper phthalocyanine of formula: [Cu Pc tris (CH.sub.2 NC.sub.3 H.sub.7 -iso)].
This phthalocyanine suffers from the disadvantage of not being depositable in organized monomolecular layer form. Therefore the performance characteristics of the detector are reduced and the reactions between the chemical species to be detected and the active molecules are limited to adsorption or desorption phenomena on the molecular sites of the surface of the film.